The political and economic crisis in Ukraine threatens to disrupt vital Russian gas supplies to Europe for the third winter in a row, senior European commission officials warned today.

Their warning came as the head of Gazprom, Russia's main producer, blamed Ukraine for a potential disruption to supplies in transit through the crisis-torn country.

Ukraine, bailed out with a $16.5bn (£11.14bn) loan from the IMF and EU, owes Russia €2.3bn (£2.17bn) and is unable to pay as its economy and currency go into meltdown despite the aid.

The situation has been compounded by open warfare between President Viktor Yushchenko and his premier Yulia Tymoshenko over the causes of the crisis which has seen the hryvnia, the currency, sink to historic lows.

Andris Piebalgs, EU energy commissioner, indicated he was ready to travel to Moscow early in the new year for emergency talks with the Russians. "I am very worried," he said.

High-level talks between Brussels and Moscow have already begun and now include Kiev, the Ukrainian capital. More than 80% of Russian gas, which provides more than a quarter of Europe's needs, transits through Ukraine.

Piebalgs said he had been assured in letters from the Russians that supplies to Europe would remain intact despite the Ukrainian crisis. The two sides are due to hold a summit in Moscow in January which is designed to ease acute tensions.

But Viktor Zubkov, Russia's first deputy prime minister and Gazprom chairman, said the near-monopoly supplier had offered to redeem Kiev's debt. "So far no solution has been found because of the non-constructive position of the Ukrainian side," he stated.

The Kiev authorities insisted that they could give guarantees of uninterrupted gas supplies in 2009 to European gas consumers. But Piebalgs said their current contract with Gazprom and another supplier, Naftogaz, runs out on 31 December.

EC officials say both the Ukrainians and Europeans have substantial levels of gas storage in case of disruption but admit that, if this winter is as cold as that of 2005 - the coldest for 60 years - the reliability of supplies will be in serious question.